A very famous cannon "Mons Meg" has been associated with Norham Castle. In 1457, King James II was presented with two massive siege guns by his uncle by marriage, Philip the Good, Duke of Burgundy. The surviving gun is now called Mons Meg and it is displayed in Edinburgh Castle. ("Meg" in Scotland is one of the short forms of "Margaret").

Made in Mons in Belgium it fired missiles weighing 330lbs (150kg) over two and a half miles.

It saw action against the English at the siege of Norham Castle in 1497. But its great weight (over six tons) meant that it could only be moved at the rate of three miles a day so it was retired and used only on ceremonial occasions.